Bifocal lens.



N0. a76,9ss. PATENTED JAN. 21, 1908.

' J. L. BORSGH, JR.

BIFOGAL LENS.

APPLICATION FILED JAN. 23, 1904.

FIG 4 FIG 1.

FfCiZ FIG. 3.

FIG 10.

WITNESSES:

" J U IT D STATES PATENT OFFICE.

JOITN L. Bosses, .TR., OF'PHILADELPHIA, PENNSYLVANIA, AssIGNon, BY MESNE AssI NimNTsro KRYPTOK COMPANY, A CORPORATION OFNEW YORK.

a separate tances, or 0 cm loying lenses of the char- I QIFIFOGAL LENS.

Specification of Letters Patent.

' PatentedJan. 21,1908;

Application filed January 23. 1904. Serial No. 190.257.

To all whom it may concern:

' Be it known that; I, JOHN L. BoRscH, Jr.,

a citizen of the United States, residing in the city and county 'of Philadelphia, State of Pennsylvania, have invented certain new and useful Improvements in Bifocal Lenses,

of which the following is a specification.

.My invention relates .to lenses employed in spectacles, eye-glasses, and other optical instruments, of that class having a plurality of independent focal points. The lenses embodg ing my inventioninclude regions which are or tive indices of refraction are of dissimilar power. Lenses of this construction are employed 1n spectacles and eye-glasses by persons whose vision is of such a character that alens which enables :them to see objects located at a certain distance from the eyes does not enable them to see objects located'at a different distance, either greater or less, from the eyes. Such persons are under the necessity either of employing a plurality of pairs of glasses,

' air for different selected disacter above set orth having a plurality of distinct regions having dissimilar or different powers of refraction, and consequently a plurality of independent focal points.

. Heretofore, lenses of the latter character have been constructed of two or more separate pieces of glass, cemented together by means of a suitable cement, for instance,- Ganada balsam, the said pieces of glasshaving different indices of refraction. -Generically considered, my invention con-' sists of a lens formed of a sin le integral piece of glass having a plurality o regions'therein, of diflerent'ondissimilar refractive power,- -and my invention also comprehends or con sists in the process or method by means of which such a lens is produced In the manufacture of my lens I'maytake.

a piece of glass having suitable dimensions, the said glass being composed of ordinary lens material, such as Crown glass, and form a depression therein, and then take apiece of glass having a difierent index of refraction,

and grind the same so that it will fit in the epressijon and place it therein and subject the whole, to a temperature or heat suflicient to occasion coalescence of the two med of such material that their respec the two glasses to a temperature such as above indicated, they are fused or welded into a single, integral piece of glass.

The latter method of construction or manufacture may be employed, though the first. method referred to is preferable.

Instead of laying one piece of glass upon another, the edges of two or more pieces ofglass may be brought into contact and held ,70

in that position, while they are subjected to 'heat as above indicated, to cause the edges. J

to unite to form a single integral and omo- 4 geneous piece of glass out of which a lens may-be formed by grinding in the same manner asin the two previous constructions referred to. j

It will be understood that the lenses may be'ground to the desired curvature or form,

the same as is usual in the manufacture 8Q of spectacle, eye'- glass, and other optical .lenses.

Referring to the drawings forming a. part of thisv specification :'Figure 1 is a plan view, of a plate showing in outline a smaller portion or section of plate, the two-plates having difierent indices of refraction Figure,2 is a central tlflIlSVGISGSGCtlOD of the plates shown in Figure 1;

Figure 3 is a section of a s hericallens .90 formed from the late shown in igure 1 Figure 4 is a p an view of a'plate of glass having two-smaller ortions. or sections of glass. embedded in t 'e surface thereof, the

three pieces of glass'having dissimilar .or dif ferent indices of'refraction;

Figure 5 is atransverse sect on through the three pieces of glass shown. in Figure/1;

Figure 6 is a section of a doubleconvex lens formed from the plate shown in Figure'4; 106

Figure 7 is a section corresponding to the section shown in Figure 2, but indicating a slightly modified method of construction;

Figure 8 is a section of a double'convexlens formed from the plate shown in Figure 7;

Figure 9 is a transverse section of a spherical lens formed from a piece of glass having its edges welded or secured together by the ap lication of heat'; and,

igure 10 is a t-fansverse section of a prismatic glass having two portions of glass secured together in the same manner as is the case in Figure 9. v

In Figures 1 to 3 of the drawings,1 designates a piece of glass of a selected index of refraction having a depression 2 therein, which is adapted to receive a piece of glass 3 having a selected index of refraction different from that of the index of refraction of the main or body portion of the glass 1.- The ing process for the purpose of raising the temperature to a point sufficient to occasion the fusion or welding of the two pieces of glass together to form a single, integral piece of glass which may be ground to any curvature or form desired, as for instance spherical, as illustrated in Figure 3'.

The construction shown in Figures 4, 5, and 6 is substantially the same as that shown .;in Figures -1 to 3, the only difl erence being that two different pieces of glass 3, each having a different index of refraction, are shown as embedded in the surface of the main or body portion 1 of the glass from which the lens is formed, the said body portion having an index of refraction differing from that of the pieces 3.

formed having three inde endent focal oints, while in the form of construction:

' Illustrated in Figures 1 to 3,-inclusive, a lens is formed having two independent focal oints.

' As illustrated in Fi ure 7, themet od of manufacture is somew at different from that shown in the preceding Figures 1 to 6 of the drawings, the difference being that in the form of construction shown in Figure 7 ,the pieceof lass 4 .is laid u on the smooth surace of t e main or. b0 y portion 1 of the glass from which the lens is formed, after which the two pieces are subjected to heat in the same manner as in the constructions illustrated in Figures 1 to 6, whereby the fusing'o'r welding together of the two pieces of lass is eflected, after which the lens may be ormed by grinding to any suitable curvature or form which may be desired. The dotted lines 5 shown in Figure 7 indicate the outline faces an In the latter construction lllustrated in Figures 4, 5, and 6, a lens is of a double convex lens, such a lens being shown in full lines in Figure 8.

Figures 9 and 10 designate a form of con-- struction in whichtwo pieces of glass, 6 and p 7, each having a different index of refraction, are placed in contact edge to edge and subjected to a heat sufficient to weld or fusethe edges together to form an integral structure,

cated in Figure 10, or to any other suitable curvature orform as may be desired.

The line of junction or connection between the portions of glass of different refractive power embodied in the lenses is clearly indicated in the several figures of the drawin s.

It Wlll be understood that any suitable furnace or other means may be employed for subjecting the glass to heat to raise the same to the temperature necessary to occasion a coalescence or welding together of the separated pieces of glass in the process of lenses embodying my invention. v

Having thus described my invention, I claimz-- Y vafter which they may be ground spherical, as indicated in Figure 9, prismatic, as indi-' manufacturing eye-glass or other optical 1. An optical glass lens consisting of an integral piece of glass ground with even surhaving a plurality of independent focal points.

2. A spectacle, eye-glass, or other optical lens consisting of an integral piece of glass, diflerentindices 0 refraction.

3. A spectacle, eye-glass, or other optical lens consisting of a body portion having a selected index of refraction, and one or more as I ortions of which have diflerent portions of glass embedded in the surface of the said body ortion and integral therewith,

the said embe ded portion or portions having an index or indices of refraction different from that of the main or body portion.

'4. An optical glass lens consisting of a a main or body portion having a selected index of refraction, a lurality of portions of glass embedded in t e surface of the 1 said body portion, the said embedded portions be- 1 ing integral with the, body ortion,'said embedded portions having di erent indices of refraction the said indices of refraction be-'- ing also different from that of the main or body portion. i v

5. A lens consisting of an integral le'ce of glass, different-parts of which have lfferent indices of refraction, and merge into each other along their adjacent edges only.

6. A lens consistmg of a major part or body portion having a certain index of refraction and a minor part havin a differentindex of refraction, said parts Ieing fused or welded to each other along their adjacent edges only, and havin no overlapping por tions on the face, of eit er.

.7. A bifocal lens consisting of a body of fusion to the said body of glass or similar 10 glass. of any refractive power and a portion substance.

of glass integral therewith and having-a re- In testimony that I claim the foregoing as fractive power which is difierent from that my invention, I have hereunto si ned my 5 of said body of glass. name this 19th day of January A. 1904.

8. A bifocal lens consisting of a body of JOHN L. BORSCH, JR. glass or similar substance of any refractive In presence of power, and a portion of glass or similar sub- THOS. K. LANCASTER,

stance of different refractive power secured LAURA KLEINFELDER. 

